What's an interval and how will it help me get faster? Good questions. Intervals are segments of your workout where you pick up the pace to a certain level, hold it for a given time and then slow down/recover, just to do it again...and again... Intervals are done in the pool, on the bike and the run as well. They can be set up all kinds of ways with various recovery times between them. The subject is too big for a short post, but the point is, if you're familiar with them, how do they fit into your training plan? Are they in your training plan? They have to be for you to reach your fastest speeds. If you're not familiar, just look/research on line or ask a friend. They are pretty much a staple for experienced athletes.
Intervals are often, "faster than race pace," in the effort you put in to engage quick turnover and those fast twitch muscles of yours. They tax your high-end energy system by pushing it a bit beyond what you'll do race day, which can make race day seem a bit easier.
Intervals can also be done AT race pace and the biggest benefit from this is simply to know and feel what your ideal pace is. Swimming 100s - 500s in the pool can get you familiar with what your next swim leg should feel like pace wise. Same with running either by time (your watch if out on the roads) or at the track. Example - you want to average 8 minute miles for an upcoming 10K. You go to the track and do, say, 800s/half mile repeats hitting 4 min. per 2 laps, recover with a slow/easy half lap and then hit it again and repeat several times. You begin to understand exactly what 8 min. miles feel like. Or, you can do them faster than your race pace for the reason mentioned above. Exact same thing applies on the bike on the roads.
GPS watches/computers make this a lot easier as you can just look down and see your pace when running for example. I'm not a high-tech guy at all, but have been using my GPS watch in my races so that I know exactly what my running pace is. Sometimes I look at it and say, "Man, you're slowing down, come on, pick it up!" Other times it's, "Slow down you running fool! What are doing going this fast?? Pace yourself!" So, be sure you're including intervals, shorter and medium distance/time, to your training to become as fast as possible!